[zac]

It appears I had two issues. The wire going to the clearance lights was fouled around the a/c duct and was bare and almost broken. It snapped once and for all will I was disassembling and it was hard to figure out because what was left disappeared into the door pillar where it goes up. Also, the diagram just designates it is a taillight terminal, but it’s not the one that actually goes to the taillights. Most references say it’s blank in the harness. I’m pointing to the clearance light terminal in the picture. You can see it’s ganged to the actual taillight feed.

Messing around with my meter and the various circuits from the switch, it appeared I had a short in the actual taillight harness in back. Go figure, the truck has had a hard life and the usual poor attempts at trailer light wiring, so I’m replacing all that.

I spent a lot of time with the diagram and a multimeter. There’s more going on with the switch than I thought. The taillights have their own feed and fuse, the instruments have their own fuse, and the headlights have a separate feed and internal circuit breaker. I think it paid to take some time and sort through it rather than just randomly replacing stuff. My switch works perfectly.